The present invention relates to solid-state imaging apparatus and to imaging apparatus system using the same where an imaging signal for forming image and a control signal such as AF and AE signals for determining image taking conditions are concurrently outputted.
Those digital cameras having an optical system for optically forming object image, a solid-state imaging device for converting the optical object image into electrical signals, a recording section for recording the taken object picture image, and a display section for displaying taken image have recently become common as an image recording means or image display means similarly to the film cameras and video cameras. Particularly of the single lens reflex type digital cameras, since there is great need for instantaneously taking a still picture in the same manner as a film camera, it is demanded to reduce time from the pressing of a release switch to the taking of image.
For such reason, in the single lens reflex type digital camera, an exclusive sensor separate from a solid-state imaging device is used to acquire signals for use in control of the camera's image taking system such as AF or AE. In system of such construction, there are problems as will be described below. In particular, since an image taking luminous flux and AE and AF detecting luminous flux pass through separate optical paths from each other, there is a problem that a lowered AF and AE accuracy occurs due to an error in form at the time of temperature change resulting from a component precision error of each component, attaching error of each component, or material difference between each component.
As a means for solving such problem, the following technique is disclosed in Japanese Patent Application Laid-Open 2000-156823. Such technique will be briefly described below by way of FIG. 1 and FIGS. 2A, 2B. FIG. 1 is a diagram showing color filter arrangement, and FIGS. 2A, 2B illustrate a cross sectional structure of pixel. This solid-state imaging apparatus disclosed in the publication has pixels exclusively for AF without having color filter (those pixels represented by S1, S2 in FIG. 1) in addition to the pixels having the respective filter of R (red), G (green), B (blue) for effecting an imaging on the imaging device sensor (pixels represented by R, G, B, in FIG. 1). Of the two exclusive AF pixels S1, S2, one or first exclusive AF pixel S1 (first phase sensor) has a shielding layer 201 which is provided with an opening portion 201a deviated as shown in FIG. 2A toward one side from the center of pixel, and the other or second exclusive AF pixel S2 (second phase sensor) has a shielding layer 202 having an opening 202a as shown in FIG. 2B at a location deviated by an equal distance from the center of pixel and toward the side opposite from the exclusive AF pixel S1.
In a solid-state imaging device having the exclusive AF pixels of such construction, if focus of the camera lens for forming an image on solid-state imaging device is focused on the image plane of the solid-state imaging device, there is a coincidence between image signals of a group of pixels S1 of the row containing the first exclusive AF pixels S1 and image signals from a signal group of the pixels S2 of the row containing the second exclusive AF pixels S2. If, however, the point of focus is forward or backward from the image plane of the solid-state imaging device, a phase difference occurs between the image signals from the group of pixels S1 of the row containing the first exclusive AF pixels and the image signals from the signal group of the pixels S2 containing the second exclusive AF pixels S2.
In this manner, if AF system is a phase difference system where a pupil division is conducted on the solid-state imaging device, an error factor as described above due to construction where the solid-state imaging device and AF sensor are formed of separate device is eliminated, since the pixels for normal image taking and exclusive AF pixels (AF sensor) of the solid-state imaging device are formed of the same device.
Among AF apparatus for obtaining a focused point by an operation processing of image signals obtained from the object image formed on the image plane of the solid-state imaging device, there is an AF system of the so-called hill climbing method where the taking lens is moved toward the direction along which value for indicating the degree of focus is increased, and the moving of the taking lens is stopped when a peak position has been detected. The hill climbing method takes notice of the fact that contrast information consisting of high-frequency components in the image signals is increased as image comes closer to a focus. Such high-frequency component fetched from the imaging signals for example through a band-pass filter is detected as the signal for indicating the degree of focus.
In AF device using the hill climbing method, a contrast information (contrast value) is obtained while moving the taking lens forward or backward so as to find a position where such value is maximum. To increase the speed of AF operation, therefore, it is necessary to increase the read speed of image signals from the imaging device, that is, to increase frame rate. For this purpose, Japanese Patent Application Laid-Open hei-6-141225 discloses a method in which frame rate during AF operation is increased by reading signals only from those pixels in a partial region as shown in FIG. 3 instead of reading the signals of all pixels from the imaging device. Referring to FIG. 3, what is denoted by numeral 301 is an imaging region of the solid-state imaging device which is formed by an arrangement of a plurality of pixels 302. What is denoted by numeral 312 is AF area, and only pixels 311 denoted by hatching within it are read out to achieve high rate.